This invention relates to a hydraulic cylinder, particularly to one that can produce more than one form of mechanical motion.
It is known that hydraulic actuators can produce mechanical works of linear output motion, rotary output motion and swinging motion according to their types. However, none of the type proposed heretofore can make two or more forms of output motion, and therefore, in the case of an apparatus in which more than one form of mechanical motion is desired, the applications of such actuators are found insufficient. For example, in testing mechanical properties of a material, a different apparatus is required which is capable of making linear, rotary, spiral movements, etc., for respectively tensioning, compression, bending, and twisting a test specimen so as to determine points of failure of the material, as the hydraulic actuator associated with an apparatus can only produce one form of output motion. A mechanical arm of a hydraulically operated apparatus for carrying or conveying a load sometimes needs linear movement, sometimes rotary movement, are sometimes even spiral movement. In such apparatus, two or more types of hydraulic actuators are required for operation, and this has increased the construction cost and volume requirement. Consequently, it is desirable to make improvements on these conventional hydraulic actuators.